Process and apparatus for the manufacture of artificial silk



March 26, 1940. HARTMANN ET AL 2,194,470

PROCESS AND APPARATUS FOR THE MANUFACTURE OF ARTIFICIAL SILK Filed March19, 1957 Patented Mar. 26, 1940 PROCESS AND APPARATUS FOR THE MANU-FACTURE OF ARTIFICIAL SILK August Hartmann and Johannes Uytenbogaart,Berlin-Lichterlelde, Germany, assignors to North American RayonCorporation, New York, N. Y., a corporation of Delaware ApplicationMarch 19, 1937, Serial No. 131,942 In Germany February 6, 1934 12Claims.

The present invention relates to the manufacture of filaments ofartificial origin but more particularly has for its object to devise aprocess of and apparatus for the desulphurization of viscose rayon in acontinuous process.

In the usual methods used in the manufacture of viscose rayon with acidspinning baths, a thread is obtained after coagulation, washing, drying,etc., which contains a considerable amount of sulphur. A specialafter-treatment is required to remove this sulphur during which more orless alkaline compounds such as sodium hydroxide, sodium sulphite, soda,sodium sulphide, etc., are applied to the threads. Since theaforementioned sulphur occurs in the freshly spun thread precipitated inthe usual spinning bath in a chemically combined form as well as inphysical or mechanical suspension, a relatively strong treatment must beapplied with the chemical compounds mentioned above.

Now it has been found possible to remove, under certain conditions, alarge portion of the sulphur from the threads and to convert theremainder of the sulphur to such a chemical and mechanical state that itmay be removed by simple soaping. In addition, it has been found thatfavorable results can be achieved with this method if the removal andconversion of the sulphur takes place immediately after the coagulationof the threads in a precipitating bath which is low in acidconcentration and high in salt content, whereby the threads are notfully regenerated and the after-treatment solutions have access to andthroughout the entire thread.

The continuously progressing thread should be treated within a fewseconds, or fraction thereof, after leaving the spinning bath or whilethe sulphur is in a colloidal state.

The so-called continuous spinning process followed by an immediatewet-treatment of the thread may be adapted advantageously to this novelprocess.

The novel process is especially adaptable to the so-called continuousspinning process in which rollers, described for example in FrenchPatent No. 745,254, or the United States equivalent Patent 2,002,995 maybe used. I

It is therefore an object of the present invention to provide a novelprocess and apparatus for the desulphurization of viscose rayon.

Another object of the present invention is to provide a precipitatorybath for viscose rayon which precipitates the sulphur in the filamentsin a state which allows ready removal of the sulphur.

Still another object of the present invention is to provide anafter-treatment process for viscose rayon which removes the greater partof the sulphur therefrom.

Other objects will become apparent.

In describing the, invention reference will be made to the drawing inwhich is illustrated diagrammatically a vertical cross-section of aspinning machine.

In describing the invention reference will be made to a single unit ofthe machine. Such single units may be operated individually, or asherein illustrated, may be combined in a long row of units using commonprecipitatory tanks, coni veyor pipes, drive shafts, etc.

In the drawing the numeral l indicates a spinning nozzle from which isdrawn the thread 3.

The nozzle I is immersed in the spinning or precipitating bath 2 throughwhich the threads 3 are drawn and coagulated.

A driven roller 4 delivers the thread to the inclined treating cylinders5 and 6 over which the thread is passed in an approximately helicalpath. These rollers 5 and 6 which are inclined for a purpose to be laterexplained, are also in- 26 clined with respect to each other whereby thethread which is looped a plurality of times around the rollers is fedfrom one end of the said rollers to the other end thereof. The thread 3is then carried from the lower roller to a stationary 30 guide 1 andfrom there passes to any suitable collecting device (not shown). Thesaid thread 3 may first becarried from the rollers 5 and 6 to othertreating steps such as washing and drying before being passed to acollecting device.

A sulphuric acid solution is sprayed from the nozzle 8 which is mountedon the end of a supply pipe 9.

The sulphuric acid is sprayed onto the top roller 5 in a regulatedamount whereby it spreads in a film down over the surface of thecylinder and the loops of thread conveyed thereon. The acid flows in afilm evenly down the cylinder 5 and drips oil the lower edge thereof andis caught by a drip pan III. From the drip pan ill the spent acid is.carried off by a drain pipe II.

A supply pipe l2 carries water to a nozzle 13 which sprays the lowerroller or cylinder 6 in a regulated quantity so that no spraying of thewater results. The water flows down in an even film over the roller 6and across the thread winding to the lower edge of the roller from whereit drips into a drip pan l4. A drain pipe l5 carries off the wastewater.

By using a pair of rollers for conveying the thread through thedesulphurizing steps and treating with one liquid on one inclined rollerand with a second liquid on the second inclined roller practicallyperfect separation of the different treating fluids is obtained. Alsorecovery of the separate liquids is simple due to the inclination of thetreating rollers.

Another feature in the treating of the threads in the mannerhereinbefore described is that only small quantities of treating liquidsare necessary.

The spent sulphuric acid which is carried away bythe drain pipe ll maybe recovered by carrying it to storage tanks in which the colloidalsulphur carried by the acid may be allowed to settle. After removal ofthis sulphur, which is done by allowing it to settle out and filtering,the acid may again be used.

As an example of the process to be used in desulphurizing the viscosefilaments, the following example is given.

The viscose spinning solution is extruded 'through the spinning nozzle Iinto a precipitating bath which is preferably maintained at atemperature of about -'70 C. (preferably -60) and which consists of anaqueous solution containing about 80 to 200 gr. sulphuric acid (1.84specific gravity) (preferably about 119-121 gr.), about 240-300 gr. ofsodium sulphate, (preferably about 280-285 gr.), and about 5-25 gr. ofzinc sulphate, (preferably about 16.0-16.5 gr.), per liter. This bath,which is low in acid concentration and high in salt concentration, isused because it is necessary to keep the viscose from becoming fullyregenerated so that in the immediate after-treatment with sulphuric acidon the rollers the said acid may have full access throughout the threadto more readily wash out the collodial sulphur precipitated therein.This type of bath also produces a thread which minimizes shrinkageparticularly longitudinally and imparts a definite elastic tensionwhereby it may more readily feed along the rollers.

A further advantage to be gained by the use of such a bath is that athread is produced which is in a low hydrated state, making it an easymatter to wash out the residual acid.

Other salts which might be used in place of sodium sulphate are aluminumsulphate, magnesium sulphate, ammonium sulphate, zinc sulphate, orpotassium sulphate.

The high zinc sulphate concentration in the bath is used because thehydrated zinc groups are more slowly decomposed than the sodium groups.This has the effect of acting as a buffer against the action of thesulphuric acid on the threads. A further advantage of the high zincconcentration is that the threads which are treated thereby have deeperdyeing qualities.

The somewhat high temperature of the bath compensates somewhat for theslowness of coagulation of the viscose and at the same time results onkeeping the volume of the spin bath as near constant as possible due toevaporation.

The threads after passing through the spinm'ng bath, described above,are drawn therefrom by the drawing roller 4 and passed to the rollers 5and 6 for treatment with acid and water.

The sulphuric acid which is applied to the roller 5 is an aqueoussolution containing about to 170 gr. of sulphuric acid (preferably togr.), per liter. This sulphuric acid solution is applied to the rollerat a temperature of about 20 to 60 C. although it is preferably about 40to 45 C. and the water which is applied to the other roller 6 is at atemperature above 80 C.

In using this arrangement and sequence of baths the sulphur may beremoved from the filaments by the action of the sulphuric acid solutionwhich contacts it very shortly after the initial regeneration of thecellulose and before the regeneration of the cellulose is completed, andalso before the sulphur fiocculates or while it is .in a collodialstate. This treatment with acid may continue for a considerabledistance, i. e., 5, 15, or 20 meters.

The threads passing from the precipitating bath to the spaced roller maybe and preferably are stretched therebetween. Due to the fact that thethreads have been only partially coagulated or regenerated a moresatisfactory stretching may be given or imparted to the filament.

The sulphur while in a colloidal or semi-colloidal state and beforeflocculation thereof is easily removed physically by the acid on theroller and retained and carried away thereby. The removal of the sulphurin this state is differentiated from a chemical separation which takesplace after complete regeneration of the cellulose and flocculation ofthe sulphur. The result is a golden-yellow, dilute sulphuric acidsolution in which the sulphur is present in a collodial orsemi-collodial form, which, when the said acid solution is carried to asettling tank and allowed to stand, will settlefto the bottom of thetank. The acid may then be carried off from the top of the tank andfiltered. This acid may then be re-used.

The invention as disclosed comprises extruding a viscose solution into asetting bath which partially coagulates them and precipitates thesulphur in a form whereby the sulphur may be readily removed byimmediate treatment of the thread with a pure substantially salt-freesulphuric acid while the sulphur is still in a colloidal state, and alsoserves to further regenerate the cellulosic filaments. As the filamentsproceed under the nozzle l3 they are subjected to a washing action,whereby the acid solution and sulphur, zinc, etc., carried by it areremoved.

The application of the acid and water (preferably hot) causes the threadto shrink longitudinally and maintain the necessary tension in order tocause the filaments to be fed upwardly by the rotating rollers.

The operations are preferably conducted so as to keep the degree ofhydration of the filaments as low as possible in order that lateralshrinkage of the filaments will be minimized.

Also by maintaining the hydration at a low point a greater amount ofwater is eliminated, resulting in a more sponge-like structure andv onewhich has a higher aflinity for dye-stuffs. Thus it will absorb dyesmore readily and hold them more tenaciously.

Furthermore, the threads made as described herein will have uniformproperties, such as, uniform dyeing properties, uniform shrinkageproperties and uniform denier, strength and elongation thoughout everylength.

This application is a continuation in part of a co-pending applicationto August Hartmann et al. for Manufacture of artificial silk, Serial No.3,413, filed January 25, 1935.

It is obvious that many variations may be made in the method andapparatus described herein while utilizing the invention of the presentapplication and it is not intended to restrict the invention to theparticular descriptions or examples given herein. The terms used indescribing the invention have been used in their descriptive sense andnot as terms of limitation and it is intended that all equivalentsthereof be included within the scope of the appended claims.

What is claimed is:

1. An apparatus for continuously spinning and treating filaments ofartificial origin, comprising, a spinning nozzle, a precipitating bath,a plurality of spaced rotors over which said filaments are conveyedalternately from one to the other of said rotors in a plurality of loopsafter leaving said precipitating bath, and means to supply a differenttreating liquid to each of said rotors.

2. An apparatus for continuously spinning and treating filaments ofartificial origin, comprising, a spinning nozzle, a precipitating bath,a plurality of spaced rotors over which said filaments are conveyed inplurality of loops after leaving said precipitating bath, said rotorshaving their axes at an angle to the horizontal, and means to supply adifferent treating liquid to each of said rotors.

3. An apparatus for continuously spinning and treating filaments ofartificial origin, comprising, a spinning nozzle, a precipitating bath,a plurality of spaced rotors over which said filaments are conveyed inplurality of loops after leaving said precipitating bath, said rotorshaving their axes at an angle to the horizontal, and means to supply adifferent treating liquid to each of said rotors in such quantities thatthey will substantially vertically drip from the lower ends of saidrollers.

4. An apparatus for continuously spinning and treating filaments ofartificial origin, comprising, a spinning nozzle, a precipitating bath,a pair of spaced rollers about which the filaments are looped aplurality of times after leaving said precipitating bath, said rollershaving their axes at an angle to the horizontal, and means to supply adiiferent treating liquid to each of said rollers in such regulatedamounts that they will substantially vertically drip from the lower endsof said rollers.

5. The process of desulphurizing viscose rayon comprising treating afreshly spun viscose thread immediately after coagulation in successivelengths of a plurality of meters with a dilute and substantiallysalt-free sulphuric acid, and subsequently washing said thread withwater, said acid containing about 80 to 170 grams of H2804 per liter ofH20.

6. The process of desulphurizing viscose rayon comprising helicallywinding a freshly spun viscose thread around a pair of spaced rollers,treating said thread with a dilute and substantially salt-free sulphuricacid, and subsequently washing said thread with water, said acidcontaining about 80 to 170 grams of H2804 per liter of water.

'7. The process of desulphurizing viscose rayon comprising helicallywinding a freshly spun viscose thread around a pair of spaced rollers,applying a dilute and substantially salt-free sulphuric acid to one ofsaid rollers and applying water to the other one of said rollers, saidacid containing about 80 to 170 grams of H2304 per liter of water.

8. The process of desulphurizing viscose rayon comprising helicallywinding a freshly spun viscose thread around a pair of spaced rollerswhose axes are at an angle to the horizontal, applying a dilute andsubstantially salt-free sulphuric acid to one of said rollers, andapplying water to the other one of said rollers, said sulphuric acid andwater being applied in such amounts that they will substantiallyvertically drip from the lower ends of said rollers, said acidcontaining about 80 to 170 grams of H2804 per liter of water.

9. In a continuous process of spinning viscose rayon, the steps whichcomprise extruding a viscose solution into a buffered precipitating bathat a temperature of about 45 to 70 0. whereby a partial retardeddecomposition of said viscose solution into regenerated cellulosecontaining colloidal sulphur is effected, substantially removing saidsulphur from said cellulose by applying thereto a substantiallysalt-free sulphuric acid solution at a temperature of about 20 to 60 C.

- and subsequently washing said regenerated cellulose with water havinga temperature of at least 80 C., said precipitating bath containingabout 80 to 200 g. of H2804 and about 245 to-325 g. of soluble salts perliter of water, and said salt-free sulphuric acid solution containingabout 80 to 170 g. of H2804 per liter of water.

10. In a continuous process of spinning viscose rayon, the steps whichcomprise extruding a viscose solution into a buffered precipitating bathat a temperature of about 45 to 70 C. whereby a partial retardeddecomposition of said viscose solution into regenerated cellulosecontaining colloidal sulphur is eifected, substantially removing saidsulphur from said cellulose by applying thereto a substantiallysalt-free sulphuric acid solution at a temperature of about 20 to 60 C.and subsequently washing said regenerated cellulose with water having atemperature of at leastv 80 C., said precipitating bath containing about80 to 200 g. of H2804, about 5 to g. of zinc sulphate and about 240 to300 .g. of sodium sulphate per liter of water, and said salt-freesulphuric acid solution containing about 80 to 170 g. of H2804 per literof water.

11. In a continuous process of spinning viscose rayon, the steps whichcomprise extruding a viscose solution into a buffered precipitating bathat a temperature of about 45 to 70 0. whereby a partial retardeddecomposition of said viscose solution into regenerated cellulosecontaining colloidal sulphur is effected, substantially removing saidsulphur from said cellulose by applying thereto a substantiallysalt-free sulphuric acid solution at a temperature of about 20 to 60 C.and subsequently washing said regenerated cellulose with water having atemperature of at least 80 0., said precipitating bath containing about119 to 121 g. of H2804 and about 296 to 301.5 g. of dissolved salts perliter of water, and said salt-free sulphuric acid solution containingabout 80 to 170 g. of H2504 per liter of water.

12. In a continuous process of spinning viscose rayon, the steps whichcomprise extruding a viscose solution into a bufi'ered precipitatingbath at a temperature of about 45 to- 70 C. whereby a partial retardeddecomposition of said viscose solution into regenerated cellulosecontaining colloidal sulphur is effected, substantially removing saidsulphur from said cellulose by applying thereto' a substantiallysalt-free sulphuric acid solution at a temperature of about 20 to 60 C.and subsequently washing said regenerated cellulose with water having atemperature of at least 80 0., said precipitating bath containing about119 to 121 g. of H2304, about 16.5 g. of zinc sulphate and about 280 to285 g of sodium sulphate per liter of water, and said salt-freesulphuric acid solution containing about 80 to 1'70 g. of H2304 perliter of water.

AUGUST HAR'I'MANN. JOHANNES UY'IENBOGAART.

